Bits and Pieces

A Conundrum

The following from Paul Ireland:

“I have been discussing the issue of the petrol height in the jets of the SU carbs. One point was raised: what about hills?

On consideration, I am amazed our cars are able to drive up any hills at all!

Consider an extreme example a 1:4 hill. (say ~25^o slope). This affects the carburettors in two ways.

1. The weight of the suction piston is not acting directly downwards. For a fixed weight piston this reduces its weight from 240gm to 232gm. This means that for a given airflow, the piston is floating higher, the pressure difference between the choke and atmospheric is less and the carburettor is delivering a weaker mixture. Carburettors with lighter pistons and springs are still affected but to a lesser extent.
2. The centre of the float chamber is 60mm from the centre of the jet. On the front carburettor the float chamber is 14mm (about ½”) higher than its horizontal position. Similarly, the rear float chamber is 14mm lower. Even with the fuel level 3/8” below the top of the jet (when horizontal), the front carb will flood. In the rear carb the fuel level will be 7/8” of an inch below the jet, which coupled with the reduced pressure difference in the choke means it will probably not deliver any petrol at all!

Clearly this is not the case as I used to drive my TC up a 1:4 hill quite regularly when I was young on the way back from seeing my girlfriend (now my wife).

An interesting dilemma.”

‘Drive a TC and you never know where it will lead’

This is TC0663 filming “Darling Buds of May” July 1990 – David Jason in his usual sweet talking guise.

Owner, Martin Franklin, who still has the car, recalls that it was ‘a nice little earner’ which paid for an 8:37 crown wheel and pinion from Roger Furneaux, or possibly new rear hubs and tapered half shafts.

T-Type seat back spring interiors

Wade Spring Company in Nottingham https://wade-spring.co.uk/ are predominantly a furniture spring company, but they also have patterns for TA, TC and TD. If you go to their website and look under ‘Transport Solutions’ and then sub heading ‘Vintage Car Seating’ you will find that they cater for several models.

My thanks to Brian Slater for this information.

TD/TF – Jacking up the rear of the car

The Operation Manual tells you to place the screw type jack under the rear spring, close to the axle.

Always a risky business, I feel – so I use a small block of wood with a hole drilled in it. It fits snuggly between the ‘jaws’ (is that the correct terminology?) of the jack and the U-bolt nuts and registers with the nut from the centre bolt that goes through the spring leaves. It just feels that little bit more secure, but of course, it’s still important to place supports under the axle.

Fitting an anti-roll bar to an MG TD

The following was received from Dieter Wagner:

“It is really a good idea to fit such an improvement to an MG TD. If the bar is fitted as delivered by Moss the legs of the bar go over the tie rods and the angle of the rods will be about 45 degrees. That means the effect of the bar is only at 50%. If you want to gain the full benefit of the bar (100%) it must sit horizontally. For that you must shorten the vertical links. It is very important that the length of the links is not longer than 20mm. Otherwise the bar contacts the steering linkage in extreme driving situations, such as full steering lock and very uneven road conditions. This is easy to check when the car is lifted up under the chassis and the steering is turned all the way to the end lock. The pics show how I configured my TD.”

Extended mirror bracket

Laurent Castel (TD south of France) e-mailed to say that he was grateful to receive the April issue of TTT 2 to read during the ‘lockdown’, which set his mind thinking what could he contribute for the June issue. The following, which he originally wrote for the MG car forum is the result.

Originally, the side rear view mirror was on the front wing. It is found not easy to adjust and offer a narrow view angle. Nowadays we are more used to fit side mirrors on the windscreen pillars. One can drill and tap the pillars but I know many of us won’t do such non return changes. It is also common practice to use the slotted hole of the windscreen post to fit the mirror, but it prevents folding the windscreen down. It also often interferes with the side screen when opening the door.

I designed this special bracket that uses the existing holes and screws, not foul the side screen and allow to change the windscreen position. Built in 2mm thick stainless-steel sheet that once thoroughly polished shines like chrome. (dimensions in the drawing are in mm).

Remove the washer from the original fitting of the pivot and replace by the bracket.

It is also possible to bend a little bit the upper end to clear the pillar from the mirror. The small thickness of the bracket does not prevent the door to close with the side screen.

1977 was a good year for wine corks! Picture from Alan Taylor, New South Wales (TA1939).

TB/TC Heatshields (John James)

I have just three of these left in stock which were supplied to me by Barrie Jones. They are made from stainless steel and are priced at £16, plus postage. Barrie has moved away from Cornwall, so has lost his manufacturing contact, and there will be no more. When they are gone, they are gone!

To fit this shield to the TB/TC you will also need the aluminium spacers (1/2” thick) shown in the photo (at £6.50 per spacer) and extra gaskets. This in turn will require longer exhaust manifold bolts (not supplied).

From the manifold, the sequence is:

Gasket, spacer, gasket, heat shield, gasket, carburetter.

The shield will not fit if you have a 5-speed conversion with the engine moved forward.

Some questions have been asked about the use of aluminium for the spacers. Here is Barrie’s explanation of the theory behind his design:

“The main problem with modern fuel seems to be the Ethanol content. This apparently slows down the burn so that the partially-burnt fuel continues to burn after it has been ejected from the engine. This raises the temperature of the exhaust manifold, and the radiated heat could boil the fuel in the float chambers.

The TC/TD float chambers are very close to the exhaust manifold, so:

1) The polished stainless steel reflects the heat away from the float chambers.

2) The spacers move the float chambers further away from the exhaust manifold, reducing the effects of radiation even more.

There is a secondary problem.  When Ethanol vaporizes as it exits the jets of the SU carbs, this has a refrigerant effect.  On a cold, damp morning it could cause any water vapour in the air to freeze, blocking the jets with ice.  This happens in aircraft.  Pilots are taught that icing-up of a carburetter can happen with air temperatures as high as 20°C (68°F).  So, by making the spacers from alloy I am trying to get MORE heat to the carb body whilst I am trying to get LESS heat to the carb float chambers.”

I don’t get much feedback from owners who have fitted these shields but here’s one:

…….” It has really done the trick.  I went for the first long run of the season today.  No overheating or trouble re-starting – Excellent!”

Here’s a couple of pictures of a shield supplied in January to Martin Wollacott:

To order, please send an e-mail to me jj(at)ttypes.org [please substitute @ for (at)] or write to 85 Bath Road, Keynsham, BRISTOL BS31 1SR or telephone 0117 986 4224. UK postage is 3.10 GBP.